Systems and methods for calibrating light output by light-emitting diodes

ABSTRACT

A system and method for calibrating light output from an LED is provided. The system includes a support on which an LED is positioned, a photosensor to measure the light output from the LED, and means for calibrating and adjusting the light output of the LED. Calibration is accomplished by measuring the light output from the LED, comparing such output against a reference value, and adjusting the measured output against the reference value.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit, under 35 U.S.C. §120, as acontinuation of U.S. Non-provisional application Ser. No. 10/842,242,filed May 10, 2004, which in turn claims priority to U.S.Non-Provisional application Ser. No. 09/675,419, filed Sep. 29, 2000,which in turn claims priority to U.S. Provisional Application Ser. No.60/156,672, filed Sep. 29, 1999. Each of the foregoing applications ishereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to light-emitting diodes, andmore particularly, to systems and methods for calibrating illuminationoutput generated by light-emitting diodes.

BACKGROUND

Light-emitting diodes (LEDs), when disposed on a circuit, acceptelectrical impulses from the circuit and convert the impulses into lightsignals. LEDs are typically energy efficient and can have a longlifetime.

Various types of LED exists, including air gap LEDs, GaAs light-emittingdiodes, polymer LEDs, and semi-conductor LEDs, among others. Althoughmost LEDs in current use are red, LEDs may take any color. In addition,when several LEDs, each of a commonly used primary color—red, blue orgreen—are combined in different proportions, the combination cangenerate almost any color in the visible spectrum in response tochanging electrical signals. Alternatively, a single LED may be designedto include dies, each with a primary color (i.e., red, blue, and green),which can be combined to generate almost any colors.

Traditionally, LEDs have been poor in their ability to generatesufficient light output for illumination. Accordingly, LEDs have beenused in low light environments, such as a flashing light on a modem orother computer components, or as a digital display of a wristwatch.However, over the past several years, the ability of the LEDs togenerate sufficiently high intensity light output has increasedsubstantially. Thus, LEDs have recently been used in arrays forflashlights, traffic lights, scoreboards and similar displays, and astelevision displays.

Despite this new development, the manufacturing of high-intensity LEDs,is still a challenging process. In particular, it has been difficult toprecisely predict the performance of an LED-based product in terms oftotal light output and quality of the output. Specifically, as an LEDincreases in output intensity, the quality of the output decreases.

In general, during manufacturing, the LEDs are tested for total lightoutput and subsequently classified into “bins”. Depending on themanufacturer, however, this classification can happen either after thesemiconductor wafer has been sliced into individual dies or after thedie is packaged into the LED plastic housing. In either case, for eachLED, a light output determination is made of both wavelength (the colorof light) and intensity of the output. The LEDs are then sorted and soldbased on the bin-type for which they have been classified.

It should be noted that even with bin sorting, there remain substantialand perceptible differences in the light output amongst LEDs. Thisdifference, as a result, can lead to perceptible differences in lightoutput between otherwise identical LED-based products. Moreover, if“additive mixing” is employed, wherein a few LEDs of different colorsare mixed to produce other colors, should the color in one or more ofthese LEDs be off, then the results of the additive mixture will also beoff.

Furthermore, the light output from the LEDs may change over time as aresult of a variety of factors, and can also contribute to perceptibledifferences in light output. For instance, the LEDs may degrade or shiftin color output over time, as part of a normal deterioration of theLEDs. In addition, long term exposure of the LEDs to high heat, orrequiring the LEDs to maintain high intensity light output over anextended period of time, such that the LEDs produce too much heat, or ifthe heat can not be removed sufficiently quickly away from the LEDs,such effects can accelerate the deterioration of the LEDs and lead topermanent changes in the LEDs.

Accordingly, it is desirable to provide a system which can calibrate andadjust the light output of each LED, so that uniformity in light outputby the LED can be achieved, during manufacturing, and subsequentlymaintained during the lifetime of the LED, either alone or incombination.

SUMMARY

The present invention, in accordance with one embodiment, provides amethod for calibrating light output by a light-emitting diode (LED). Themethod includes generating light output through the LED. Subsequently,measurement of the light output generated by the LED is obtained.Thereafter, the light output measurement is compared to a referencevalue designated for an LED of the type similar in classification (i.e.,from the-same bin) to the LED being calibrated. Once the comparison ismade, if there are any differences between the light output measurementand the reference value, the light output of the LED being calibrated isadjusted against the reference value. A calibration value is thereafterformulated from the adjustment of the output measurement against the5reference value. Subsequently, the calibration value may be stored in amanner which permits access by the calibrated LED, so that upon asubsequent generation of light output, the calibration value may beaccessed to permit the calibrated LED to generate alight output thatapproximates an output accorded to the reference value. The lightoutput, may be calibrated to adjust the intensity of the output, as wellas the color of the output by the LED. It should be noted that thecalibration protocol of the prevention invention may be implemented inan environment where there is an existence or absence of ambient light.

In another embodiment, the present invention provides a system forcalibrating light output by an LED. The system, in one embodiment,includes a support to which an LED to be calibrated may be positionedthereon. The system further includes a photosensor, placed in a mannerwhich permits receipt of light output by the LED, for obtaining anoutput measurement from the light output. The system further includes aprocessor in communication with the photosensor and for formulating acalibration value from an adjustment of the output measurement against areference value. The processor may also be in communication with the LEDfor transmitting thereto a resulting value from the calibration. Amemory mechanism may be provided in association with the LED on whichthe resulting value from the calibration may be stored for subsequentaccessed during light output generation by the LED.

The present invention also provides a calibration device for calibratinglight output from an LED. The device includes a support to which an LEDto be calibrated may be positioned thereon, and a photosensor adjacentto the support for obtaining an output measurement generated by the LED.The device further includes a communication mechanism through which anoutput measurement from the photosensor may be communicated to aprocessor for formulation of a calibration value, and through which thecalibration value may subsequently be communicated to the LED and storedon a memory device coupled to the LED. The device, in one embodiment,may be a handheld device, and may include a display to provide to a userstatus of the light output of the- LED being calibrated. The device mayalso include an interface to permit the user to vary light outputparameters for the LED; and a memory mechanism for storing the outputmeasurement from the photosensor, which output measurement cansubsequently be communicated to an off-site processor for calibrationprocessing. In an alternate embodiment, the device includes acalibration processor for therein for prompt and efficient calibration.

In accordance with another embodiment, a calibration device is providedfor calibrating light output from an LED, while permitting the LED toremain within its illumination device (i.e., the LED does not have to beremoved from the light fixture for calibration). The calibration deviceincludes a housing, an activation unit for inducing light output from anLED to be calibrated, and a photosensor at one end of the housing forobtaining an output measurement from the light output generated by theLED. The calibration device also includes a communication mechanism inthe housing through which output measurement from the photosensor can becommunicated to a processor for formulation of a calibration value, andthrough which the calibration value may subsequently be received by thedevice and subsequently communicated to the LED in the illuminationdevice. The device, in one embodiment, may be a handheld device, and mayinclude a display to provide to a user status of the light output of theLED being calibrated, an interface to permit the user to vary lightoutput parameters for the LED. The device may also include a memorymechanism for storing the output measurement from the photosensor, whichoutput measurement can subsequently be communicated to an off-siteprocessor for calibration processing. In an alternate embodiment, thedevice includes a calibration processor.

The present invention further provides an illumination device having ahousing, an LED illumination source within the housing, and aphotosensor adjacent to the LED illumination source to obtain an outputmeasurement generated by the LED illumination source. The device alsoincludes a processor within the housing and in communication with thephotosensor for calibrating the output measurement from the photosensoragainst a reference value. The processor in also in communication withthe LED for transmitting thereto a resulting calibration value from theprocessor. The device further includes a memory mechanism coupled to theLED illumination source and on which the resulting calibration valuefrom the processor may be stored. The device may also include a-displayon which parameters regarding light output from the LED illuminationsource may be provided to inform a user of the status of the lightoutput, and an interface to permit the user to vary the light outputparameters.

BRIEF DESCRIPTION OF THE DRAWINGS

The various advantages of the present invention will become apparent toone skilled in the art by reading the following specification andappended claims and by referencing the following drawings in which:

FIG. 1 illustrates, in accordance with an embodiment of the presentinvention, a system for calibrating light output from a light-emittingdiode.

FIG. 2 illustrates schematically calibration of light output inaccordance with an embodiment of the invention.

FIGS. 3A-B illustrate representative color peaks generated from an LEDbefore calibration and after calibration.

FIG. 4 illustrates, in accordance with an embodiment of the presentinvention, a device for calibrating light output from a light-emittingdiode.

FIG. 5 illustrates, in accordance with another embodiment of theinvention, a device for calibrating light output from a light-emittingdiode.

FIG. 6 illustrates, in accordance with one embodiment of the invention,an illumination device capable of calibrating the light output of itslight-emitting diodes.

DETAILED DESCRIPTION

Referring now to the drawings, in FIG. 1, there is shown a system 10 forcalibrating light output from a light-emitting diode (LED). The system10, in one embodiment, includes a support 12, on which one or more LEDs13 to be calibrated may be positioned. The support 12 may alsoaccommodate a module (not shown) with one or more LEDs 13 therein,similar to those modules used in connection with various LEDillumination devices. Such a module is disclosed in U.S. Pat. No.6,016,038, which is hereby incorporated herein by reference.

The system 10 also includes a photosensor 14 for measuring thephotometric output (i.e., light output) the LED 13. For the ease ofdiscussion, reference will be made to a single LED 13, with theunderstanding that the system 10 is capable of calibrating-multipleLEDs. The photosensor 14, may be placed in any location relative to theLED 13, so long as the photosensor 14 can receive the output by the LED13. Accordingly, the photosensor 14 may, for instance, be adjacent tothe LED 13, or in substantial alignment with the LED 13, as illustratedin FIG. 1. An example of a photosensor which may be used in connectionwith the system 10 for obtaining an output measurement from the LED 13is a photosensor manufactured by Ocean Optics Device, which can measurethe color output, as well as intensity of the output.

In addition to a photometric sensor, other types of sensors may be usedto measure the light output of the LED 13. Examples of sensors which maybe used include, but not limited to, a photometer, spectrophotometer,spectroradiometer, spectrum analyzer, spectrometer, CCD, photodiode,photocell, and thermocouple.

A processor 15 may be provided in communication with the photosensor 14to calibrate and adjust the output measurement received from thephotosensor 14 against a reference value for intensity and/or color forsuch an LED. (A detailed description of the calibration process will bedescribed hereinafter below.) The processor 15 may also be incommunication with the LED 13, so as to transmit to the LED 13 acalibration value (obtained from the calibration and adjustment of theoutput measurement against the reference value) for adjusting theultimate output by the LED 13, whether such adjustment is with respectto intensity or color. It should be appreciated that the calibrationvalue, when taken into account during periods of light output by the LED13, subsequent to the calibration, permits the light output from the LED13 to approximate an output accorded to the reference value.

As LEDs are highly responsive to changing electrical signals, i.e.,changes in the LED color and intensity state may be quite rapid inresponse to changing electrical signals, the processor 15 may becontrolled by, for example, a computer program, to send the appropriateelectrical signals to the LED 13 being calibrated. The signals from theprocessor 15 sent to the LED 13 may also be digital in nature, so thatcalibration of the LED 13 may be as precise as possible. As shown inFIG. 1, the processor 15 may be part of computer. However, it should beappreciated that the processor 15 may be part of any device capable ofproviding the processor with appropriate signals.

The system 10 further includes a memory mechanism 17 in association withthe one or more LEDs 13, and on which the calibration value for use inadjusting the light output by the one or more LEDs 13 is stored. Memorymechanism 17 may be any commercially available memory mechanism havingdata storing capability. In one embodiment of the invention, the memorymechanism 17 is physically coupled to the one or more LEDs 13, so thatonce the calibration value has been stored thereon, the memory mechanism17 can be removed from the support 12 along with the one or more LEDs13. Upon subsequent generation of light output from the LED 13 in, forexample, an illumination device, the calibration value on the memorymechanism 17 can be accessed to affect the output generated from the LED13. In other words, the calibration value permits the light output fromthe LED to approximate light output accorded to a reference value forthat type of LED.

Still referring to FIG. 1, the system 10, in accordance with oneembodiment of the present invention, includes a housing 16 extendingfrom the support 12 to the photosensor 14. The housing 16, I oneembodiment, may be an enclosed structure configured to encompass thesupport 12 and the photosensor 14, so as to block ambient light frominterfering with measurement of the LED light output by the photosensor14 during calibration. The housing 16 may also be provided with anopening 18 through which the LED 13 can access within the housing and bepositioned on the support 12.

As shown in FIG. 1, communication between the processor 15 and either ofthe LED 13 or the photosensor 14 can be implemented by a cable 19.Alternatively, a wire, network, or a combination thereof may be employedin place of cable 19. It should be appreciated that communicationbetween the processor 15 and either of the LED 13 or the photosensor 14can be by wireless means, including but not limited to, radio frequency(RF), infrared (IR), microwave, electromagnetic transmission, acoustic,Bluetooth, home RF, or other wireless means.

The system 10 can be used to calibrate light output, such as lightintensity, from an individual LED or multiple LEDs. Alternatively, thesystem 10 can be used to calibrate the color illumination of an LEDhaving multiple color dies, or multiple LEDs, each of different color.The need to calibrate the color illumination can be important,especially when color mixing is involved, where the cumulative output ofthe individual die in one LED, or of multiple color LEDs can be affectedby any perceptible differences between the dies or LEDs of the samecolor. For example, when Red, Green and Blue dies are used in one LED orwhen groups of Red, green and Blue LEDs are used to generate a range ofcolor within a color spectrum, including white light, even afterappropriate circuit implementations, if there are any malfunctioningdies or LEDs, those malfunctioning dies or LEDs can generate verydifferent light intensity and color outputs, thereby affecting theoverall light output. These differences can often seen in older LEDs(i.e., after the LEDs have been in use for some time), and can sometimebe observed in new LEDs, even in those newly manufactured. Accordingly,it is useful to calibrate newly manufactured LEDs or recalibrate usedLEDs, so that a desired light output can be achieved.

Calibration may be accomplished, in an embodiment, through the use ofphotosensor 14. As shown in FIG. 1, the photosensor 14 and LED 13 can bepositioned within the housing 16 along axis X and facing towards oneanother. Although the photosensor 14 and the LED 13 can be in alignment,it should be appreciated that their position relative to one another canbe in any arrangement, so long as the photosensor 14 is capable ofreceiving the light output from the LED 13 in a uniform manner.

Referring now to FIG. 2, a process for calibrating light output is showntherein. Once the LED 13 is in position for calibration, as indicated initem 21, the LED 13 may be caused to generate a light output 22. If oneor more LEDs 13 are being calibrated, each LED in the group may becaused to generate light output in sequential fashion. As each LED 13generates its light output, for example, red, green or blue, thephotosensor 14 records, in step 23, a peak measurement from the lightoutput, and assigns, in step 24, as a spectral response, a relativevalue for the peak measurement. As shown in FIG. 3A, the peak value forthe light output can vary widely. In step 25, the peak value for eachindividual output may be compared to a reference value (e.g., within atable of reference values) that had previously been established asrepresentative for an LED of that type. If there are any differencesbetween the peak value and the established reference value, the peakvalue for that individual output is adjusted, in step 26, by scalingthat individual output to the reference value. The adjustment of thelight output in this manner can result in the higher peaks being reduced(i.e., scaled) to match the value of the lower peaks, see FIG. 3B, toprovide a uniform light output. It should be noted that severaliterations (i.e., adjustments) may be needed to get an adjusted peakvalue that closely resembles the reference value. Moreover, in asituation wherein calibration of a plurality of LEDs is required, oncecalibration for one LED is completed, calibration for the next LED canbe initiated.

In adjusting the output, a calibration value may be formulated. Thecalibration value for the light output of each LED 13 may then bestored, in step 27. This calibration value, once stored, can replaceprevious calibration settings, if any, and can be employed in allfuture/subsequent generation of light output by the LED 13. Storage ofthe calibration value can be accomplished by providing the LED 13 with amemory mechanism 17, such as a memory chip (see FIG. 1). In this manner,when commands are sent to the LED 13 for generating alight output, thestored calibration value for that particular LED may be accessed fromthe memory chip and used to permit the LED 13 to generate a light outputwhich approximates a light output accorded to the reference value.

As indicated previously, the system 10 of the present invention may beused to adjust differences in the color output by an LED 13 whencompared against a reference output. In addition, the system 10 may alsobe used to adjust the intensity of the light output by an LED.

The system 10 can further be used to check and/or diagnose a variety ofother potential problems by analyzing the light output of the LED. Forexample, the system 10 can check to see whether the light outputintensity of an LED is not in compliance with the reference outputvalue. If such is the determination, the finding can indicate a circuitproblem, missing LEDs, or LEDs incorrectly placed during the assemblyprocess.

The system 10 may also be used to determine if there have been any LEDplacement errors during the LED board assembly. In particular, adiscrepancy between a measured color value and referenced color valuemay indicate that one or more of the LEDs may have been placedimproperly, e.g., a green LED in a red location or some other incorrectcombination, during assembly.

If a substantial hue difference is detected, such may indicate that aparticular run/batch of LEDs may have been improperly made, resulting inoff-color LEDs.

The information obtained when employing the system 10 can also be usedto identify problematic trends in the LED manufacturing process. Forinstance, the information may be use to determine whether the overalloutput by the LEDs is changing (i.e., deteriorating over time) for eachbatch of LEDs produced by comparing the initial information logged onthe computer running the calibration software against the informationfrom the latest batch.

As a note, should photosensor 14 or any of the listed sensors becomeunavailable, the system 10 is designed so that human eyes may beemployed in the calibration, where a user could employ the processor 15to calibrate the light output from the LED according to his subjectivesettings.

Looking now at FIG. 4, FIG. 4 illustrates, in accordance with anembodiment of the present invention, a device 40 for calibrating lightoutput from a light-emitting diode. The device 40 includes a support 41,to which an LED 42, for instance, newly manufactured, or from anillumination device (not shown), may be positioned thereon forcalibration. The device 40 also includes a photosensor 43 adjacent tothe support 41 for obtaining an output measurement generated by the LED.The photosensor 43 may be placed in any location relative to the LED 42,so long as the photosensor 43 can receive the output by the LED 42.Accordingly, the location of the photosensor 43 may be adjustable withinthe device 40, so that for example, the photosensor 43 may be movedadjacent to the LED 42, or into substantial alignment with the LED 42.

The device 40 further includes a communication mechanism, such as port44. The port 44 may be designed to be in coupling communication with thephotosensor 43, so that an output measurement from the photosensor 43may be communicated to a processor 45 for formulation of a calibrationvalue. The port 44 may also be designed to be in coupling communicationwith the LED 42, so that data, such as the calibration value, from theprocessor 45 may be received and relayed to the LED 42.

Communication between the processor 45 and the port 44 may be byconventional cables 46, or by wires, network or a combination thereof.Alternatively, communication between the processor 45 and the port 44may be by wireless means 47. Such wireless means include, but are notlimited to, RF, IR, microwave, electromagnetic transmission, acoustic,Bluetooth, home RF, or other wireless means.

In employing wireless communication means, the port 44 may be providedwith a transmitter 48, coupled to the photosensor 43, and a receiver 49,coupled to the LED 42.

Alternatively, the port 44 may be provided with a transceiver (notshown). The transmitter 48 and receiver 49 used in connection with thepresent invention are those commercially available, and of the type forreceiving the signals provided herein.

It should be appreciated that the calibration value received from theprocessor 45 through the port 44 may be forwarded to the LED 42, andsubsequently stored on a memory mechanism 491 in association with theLED 42. The memory mechanism 491, in one embodiment, may be physicallycoupled to the LED 42. The calibration value, as noted earlier, may beused in adjusting the light output of the LED, so that the light outputapproximates an output accorded to a reference value against which thecalibration value was formulated.

The device 40, in one embodiment, may be a handheld device, and mayinclude a display 492, on which parameters regarding light output fromthe LED 42 may be provided to inform a user of the status of the lightoutput from the LED 42. The display 492 may provide information such asflux, candle power, energy, luminescence, color, CCT, CRI, x-coordinate,y-coordinate, or any other measurable parameter. The device 40 may alsobe provided with an interface 493 to permit the user to vary lightoutput and/or parameters for the LED. In an alternate embodiment,instead of providing the device 40 with display 492 and user interface493, information regarding the light output may be communicated throughthe port 44 to a unit having processing and display capability, such asa computer 45, to permit display and adjustment of the light output andthe parameters from the LED 42. Communication of the information throughthe port 44 can be by conventional cables or by wireless means, asprovided above.

The device 40 may also include a memory mechanism 494, separate from thememory mechanism 491 coupled to the LED 42. The memory mechanism 494 maybe used for storing the output measurement from the photosensor 43 andother light output parameters, all of which can subsequently becommunicated to an off-site processor 45 for calibration processing. Inan alternate embodiment, the device 40 may incorporate the processor 45within the device 40 to permit, for example, calibration to be carriedout in a timely and efficient manner, without the need to communicatewith an off-site processor.

Once the calibration is completed, the process stops and the LED 42 maybe removed and returned to its illumination device.

In FIG. 5, another calibration device 50 is provided, in accordance withan embodiment of the present invention. The device 50 is similar to thedevice 40, illustrated in FIG. 4, except that the device 50 can beconfigured to calibrate the light output of one or more LEDs 13, withouthaving to remove the one or more LEDs 13 from the illumination device 52within which the one or more LEDs sit.

The calibration device 50, as shown in FIG. 5, includes a housing 51 anda photosensor 53 at one end of the housing 51 for obtaining an outputmeasurement from the light output generated by the one or more LEDs 13.The photosensor 53 may be affixed at one end of the housing 51, or maybe adjustable to alter its position within the housing 51. As the one ormore LEDs will remain within the illumination device 52 and will not bepositioned on the device 50 during calibration, the calibration device50 may be provided with an activation unit 54 for inducing light outputfrom the one or more LEDs 13. To activate the one or more LEDs 13 togenerate alight output, the activation unit 54 may send a signaldirected at the one or more LEDs 13. To this end, the illuminationdevice 52 or the one or more LEDs 13 themselves may be designed with theability to receive the signal from the activation unit 54. The signalfrom the activation unit 54 can be sent by conventional cable orwirelessly. In the wireless embodiment, the device 50 may include atransmitter 55 coupled to the activation unit 54 to transmit the signal.Correspondingly, the illumination device 52 can be provided with areceiver (not shown) coupled to the one or more LEDs 13 to receive thesignal transmitted from the activation unit 54.

The calibration device 50 may also include a communication mechanism,such as a port 56, in the housing 51, similar to port 44 in device 40.In particular, the port 56 maybe designed to be in couplingcommunication with the photosensor 53, so that an output measurementfrom the photosensor 53 may be communicated to a processor 57 forformulation of a calibration value. The port 56 may also be designed sothat data, such as the calibration value, from the processor 57 may bereceived by the device 50, and subsequently relayed to the one or moreLEDs 13. The port 56 may employ conventional cables for communication ormay employ wireless means, such as a transmitter or receiver, asdescribed above. In one embodiment, the transmitter in connection withthe port 56 and transmitter 55, used to transmit activation signals tothe one or more LEDs 13, may be a single transmitter.

The device 50, in one embodiment, may include a display 58, on whichparameters regarding light output from the one or more LEDs 13 may beprovided to inform a user of the status of the light output from the oneor more LEDs 13. The device 50 may also be provided with an interface 59to permit the user to vary light output and/or parameters for the one ormore LEDs. The device 50 may also include a memory mechanism 591. Thememory mechanism 591 may be used for storing the output measurement fromthe photosensor 53, as well as other light output parameters, all ofwhich can subsequently be communicated to an off-site processor 57 forcalibration processing. In an alternate embodiment, the device 50 mayincorporate the processor 57 within the device 50 to permit, forexample, calibration to be carried out in a timely and efficient manner,without the need to communicate with an off-site processor.

Looking now at FIG. 6, the present invention further provides anillumination device 60 which may be capable of self calibration. Thedevice 60 may be similar to the module in U.S. Pat. No. 6,016,038, andincludes a housing 61, and an LED illumination source 62 including oneor more LEDs 13 within the housing 61. A photosensor 63 may bepositioned adjacent to the LED illumination source 62 to obtain anoutput measurement generated by the LED illumination source 62. Theposition of the photosensor 63 relative to the LED illumination source62, in one embodiment, permits the photosensor 63 to uniformly recordthe light output from the source 62.

The device 60 may also include a processor 64 within the housing 61 andin communication with the photosensor 63 for calibrating the outputmeasurement from the photosensor 63 against a reference value. Theprocessor 64 may also be in communication with the LED illuminationsource 62 for transmitting thereto a resulting calibration value fromthe processor 64. This calibration value may be used to affect the lightoutput of the source 62, such that the output approximates an outputaccorded to the reference value. In one embodiment, the calibrationprocess may be part of a feedback loop where the processor 64 monitorsthe light output from the source 62 via the photosensor 63 andautomatically communicates the calibration value to the illuminationsource 62 to permit the light output to compensate for any changes.

The device 60 further includes a memory mechanism 68 coupled to the LEDillumination source 62 and on which the resulting calibration value fromthe processor 64 may be stored. In one embodiment, the device 60 mayinclude a display 65 on which parameters regarding light output from theLED illumination source 62 may be provided to inform a user of thestatus of the light output. The device 60 may further include aninterface 66 to permit the user to vary the light output parameters.

By providing the device 60 with the above components, the device 60 maybe activated to self-calibrate periodically. For instance, parametersregarding the illumination source 62 may be reviewed on the display 65.Should the illumination source 62 require calibration, the interface 66may be accessed and the calibration process initiated. Once thecalibration is completed, and the illumination source 62 can nowgenerate a light output that approximates, for example, a light outputdefined by the user by way of the interface 66, the calibration ceases.In an embodiment of the invention, the device 60 may be designed to havethe processor 64 initiate calibration, for instance, on a periodicbasis, within certain predefined intervals, or in response to aparticular condition, so that the light output from the illuminationsource 62 may be kept at a desired predefined level. Again, oncecalibration permits the illumination source 62 to achieve the desiredlight output level, the calibration ceases.

The systems, methods and devices provided in connection with the presentinvention may be used to calibrate an LED light source for a number ofreasons, including but not limited to, intensity, color (hue orsaturation), specific spectral properties, ambient conditions, internaltemperature conditions, external ambient conditions or failure feedback(such as when one or more LEDs fails to operate).

While the invention has been described in connection with the specificembodiments thereof, it will be understood that it is capable of furthermodification. For example, the calibration value, although discussed ascapable of being stored in a memory mechanism associated with the LED orin a memory mechanism on a calibrating device, can also be stored in thehousing of an illumination device, or in a stand-alone device such as acomputer. The calibration value can additionally be used as a referencevalue against which other calibration values may be adjusted against. Asa reference value, the calibration value, like other reference valuesused in the present invention, may be formatted within a table. Inaddition, reference value against which the output measurement may beadjusted can be any defined value, for example, a value obtained fromthe measurement of environmental lighting. Specifically, the photosensormay be used to take a reading of ambient light in a room. Such a readingand its associated value may be stored as a reference value.Subsequently, during calibration, the LED output may be adjusted toapproximate the ambient light condition within the room.

Moreover, the calibration procedure, in accordance with an embodiment ofthe invention, may be accomplished through a network of lightingdevices. In particular, the calibration value may be used to adjust theillumination properties of a new device so that it may be similar to theillumination properties of other devices in the network. As an example,a new lighting unit within a network can receive signals from the otherdevices to which may initiate a calibration process in the new lightingunit. Information contained in the signals such as, but not limited to,age of the illumination devices within the network, the manufacturingdate of the illumination devices, the illumination conditions of suchdevices, or combinations of parameters (such as age, manufacturing date,and previous calibration data), may cause the new lighting unit in thenetwork to initiate a calibration procedure. In particular, as the olderillumination devices in the network may be of a different quality, forexample, they have lower light output, or they may have aged anddeteriorated. By permitting the new lighting unit to calibrate, the newlighting unit would match the older illumination devices in the network.

The network of lighting units described may communicate through anycommunications method, such as but not limited to, wire, cable, network,RF, IR, microwave, acoustic, or electromagnetic communication. The unitsin the network may communicate other instructions along with thecalibration information, or the units may only communicate thecalibration information. In addition, there may be instances where thelighting units may be used in a networked fashion to allow coordinatedlighting effects. The calibration information could be communicatedusing this network or a network specifically for calibrationinformation. Moreover, the LEDs within the lighting units may also beused to communicate the calibration information to the other lightingunits, for instance, by pulsing in a particular pattern.

Furthermore, this application is intended to cover any variations, uses,or adaptations of the invention, including such departures from thepresent disclosure as come within known or customary practice in the artto which the invention pertains, and as fall within the scope of theappended claims.

1.-24. (canceled)
 25. An illumination device comprising: a plurality ofdifferently colored LED illumination sources configured to generate anadditive mixture of colored light; at least one photosensor forobtaining at least one output measurement of radiation generated by atleast some of the LED sources; a processor in communication with the atleast one photosensor for making a comparison of the at least one outputmeasurement and at least one reference value and formulating at leastone calibration value based on the comparison; and a memory mechanismcoupled to the processor and on which the resulting at least onecalibration value is stored.
 26. A device as set forth in claim 25,further including a display on which parameters regarding light outputfrom at least some of the LED sources may be provided to inform a userof a status of the light output.
 27. A device as set forth in claim 25,further including an interface to permit a user to vary light outputparameters.
 28. A device as set forth in claim 25, wherein the at leastone reference value includes a plurality of pre-programmed referencevalues that are stored on the memory mechanism.
 29. A device as setforth in claim 28, wherein the plurality of pre-programmed referencevalues are stored on the memory mechanism as a table of fixed valuesrepresentative of respective types of the plurality of LED sources. 30.A method for calibrating light output by at least one light-emittingdiode (LED), the method comprising acts of: generating light output fromthe at least one LED; obtaining at least one output measurement for thelight output generated by the at least one LED; comparing the at leastone output measurement to at least one reference value; formulating atleast one calibration value based on the act of comparing; storing theat least one calibration value in memory; recalling the at least onecalibration value from the memory during a subsequent generation oflight output; and applying the at least one calibration value to the atleast one LED such that the at least one calibration value permits thesubsequent light output to have a calibrated intensity.
 31. A method asset forth in claim 30, wherein the step of comparing includes assigninga relative value to the output measurement, such that the relative valuemay be used in adjusting the output measurement.
 32. A method as setforth in claim 31, wherein the step of formulating includes scaling thelight output, such that the relative value approximates the referencevalue to permit generation of uniform light output by the LED.
 33. Amethod as set forth in claim 30, wherein the step of formulating permitsadjustment of intensity output by the LED.
 34. A method as set forth inclaim 30, wherein the step of formulating permits adjustment of coloroutput by the LED.
 35. A method as set forth in claim 34, wherein thecalibration of color output by the LED can be used to provide a desiredoverall hue or whiteness in a multiple LED environment.
 36. Theillumination device of claim 25, wherein: the plurality of LED sourcesincludes: at least one first light source adapted to output firstradiation having a first color; and at least one second light sourceadapted to output second radiation having a second color different fromthe first color; the processor is configured to receive at least firstand second lighting commands and, based on the at least one calibrationvalue, control the at least one first light source so as to output thefirst radiation at a first calibrated intensity that substantiallycorresponds in a predetermined manner to the first lighting command, theprocessor further configured to control the at least one second lightsource so as to output the second radiation at a second calibratedintensity that substantially corresponds in a predetermined manner tothe second lighting command.
 37. The illumination device of claim 36,wherein the at least one first light source and the at least one secondlight source are arranged with respect to each other so as to mix thefirst and second radiation having the respective first and secondcalibrated intensities to produce a single calibrated color at a giventime.
 38. The illumination device of claim 36, wherein the processor isconfigured as an addressable processor to receive the at least first andsecond lighting commands via a network connection based on an address ofthe processor.
 39. The illumination device of claim 37, wherein the atleast first and second lighting commands are provided to the processorsuch that the single calibrated color produced by mixing the first andsecond radiation having the respective first and second calibratedintensities is a calibrated substantially white color.
 40. Theillumination device of claim 36, wherein the processor is configured tocontrol the at least one first light source and the at least one secondlight source using a pulse width modulation technique, and wherein theat least first and second commands represent respective duty cycles ofpulse width modulation signals used to control the at least one firstlight source and the at least one second light source.
 41. Theillumination device of claim 36, further comprising an at leastpartially transparent housing that at least partially encloses the atleast one first light source and the at least one second light source soas to mix the first and second radiation.
 42. The illumination device ofclaim 40, wherein the processor is configured as an addressableprocessor to receive the at least first and second lighting commands viaa network connection based on an address of the processor.
 43. Theillumination device of claim 36, wherein the at least one calibrationvalue includes a plurality of calibration values, and wherein theprocessor is configured to: apply at least one first calibration valueto the first lighting command to control the at least one first lightsource to output the first calibrated intensity; and apply at least onesecond calibration value to the second lighting command to control theat least one second light source to output the second calibratedintensity.
 44. The illumination device of claim 43, wherein the memorymechanism is configured to store at least the at least one firstcalibration value and the at least one second calibration value.
 45. Theillumination device of claim 43, wherein the memory mechanism includes:a first memory integrated with the at least one first light source, thefirst memory storing the at least one first calibration value; and asecond memory integrated with the at least one second light source, thesecond memory storing the at least one second calibration value.
 46. Theillumination device of claim 43, wherein the at least one photosensor isadapted to measure the first radiation and the second radiation, whereinthe at least one reference value includes a plurality of referencevalues, and wherein the processor is configured to: determine the atleast one first calibration value by comparing the measured firstradiation to at least one first reference value; and determine the atleast one second calibration value by comparing the measured secondradiation to at least one second reference value.
 47. The illuminationdevice of claim 46, further comprising a housing to enclose at least theat least one photosensor, the at least one first light source, and theat least one second light source.
 48. The illumination device of claim46, wherein the at least first and second lighting commands are providedto the processor such that a single calibrated color produced by mixingthe first and second radiation having the respective first and secondcalibrated intensities is a calibrated substantially white color. 49.The illumination device of claim 48, wherein the processor is configuredto control the at least one first light source and the at least onesecond light source using a pulse width modulation technique, whereinthe at least first and second commands represent respective duty cyclesof pulse width modulation signals used to control the at least one firstlight source and the at least one second light source, and wherein theprocessor is configured to apply the at least one first and secondcalibration values to the at least first and second commands so as toadjust the respective duty cycles of the pulse width modulated signals.50. The illumination device of claim 49, wherein the processor isconfigured as an addressable processor to receive the at least first andsecond lighting commands via a network connection based on an address ofthe processor.
 51. The illumination device of claim 36, wherein thefirst lighting command includes a first reference signal, and whereinthe processor is configured to determine at least one first calibrationvalue for the at least one first light source such that the at least onefirst light source outputs the first radiation at a first referenceintensity when the first lighting command is the first reference signal.52. The illumination device of claim 51, wherein the at least onephotosensor is adapted to measure at least the first radiation, andwherein the processor is configured to determine the at least one firstcalibration value by: applying the first reference signal to the atleast one first light source; monitoring the measured first radiationfrom the at least one photosensor; making a comparison of the measuredfirst radiation and at least one first reference value; and determiningthe at least one first calibration value based on the comparison. 53.The illumination device of claim 52, further comprising a housing toenclose at least the at least one photosensor, the at least one firstlight source, and the at least one second light source.
 54. Theillumination device of claim 51, wherein the processor is configured toapply the at least one first calibration value to at least onesubsequent first lighting command to control the at least one firstlight source to output the first calibrated intensity.
 55. Theillumination device of claim 54, wherein the second lighting commandincludes a second reference signal, and wherein the processor isconfigured to determine at least one second calibration value for the atleast one second light source such that the at least one second lightsource outputs the second radiation at a second reference intensity whenthe second lighting command is the second reference signal.
 56. Theillumination device of claim 55, wherein the at least one photosensor isadapted to measure at least the second radiation, and wherein theprocessor is configured to determine the at least one second calibrationvalue by: applying the second reference signal to the at least onesecond light source; monitoring the measured second radiation from theat least one photosensor; making a comparison of the measured secondradiation and at least one second reference value; and determining theat least one second calibration value based on the comparison.
 57. Theillumination device of claim 56, further comprising a housing to encloseat least the at least one photosensor, the at least one first lightsource, and the at least one second light source.
 58. The illuminationdevice of claim 55, wherein the memory mechanism is configured to storeat least the at least one first calibration value and the at least onesecond calibration value.
 59. The illumination device of claim 55,wherein the processor is configured to apply the at least one secondcalibration value to at least one subsequent second lighting command tocontrol the at least one second light source to output the secondcalibrated intensity.
 60. The illumination device of claim 55, whereinthe at least first and second lighting commands are provided to theprocessor such that a single calibrated color produced by mixing thefirst and second radiation having the respective first and secondcalibrated intensities is a calibrated substantially white color. 61.The illumination device of claim 60, further comprising a housing toenclose at least the at least one photosensor, the at least one firstlight source, and the at least one second light source.
 62. The methodof claim 30, wherein the act of applying comprises acts of: a)generating first radiation from at least one first LED in response to afirst lighting command, the first radiation having a first color; b)generating second radiation from at least one second LED in response toa second lighting command, the second radiation having a second colordifferent from the first color; c) processing the first lightingcommand, based on the at least one calibration value, such that thegenerated first radiation has a first calibrated intensity thatsubstantially corresponds in a predetermined manner to the firstlighting command; and d) processing the second lighting command, basedon the at least one calibration value, such that the generated secondradiation has a second calibrated intensity that substantiallycorresponds in a predetermined manner to the second lighting command.63. The method of claim 62, further including an act of: e) mixing thefirst and second radiation having the respective first and secondcalibrated intensities to produce a single calibrated color at a giventime.
 64. The method of claim 62, further including an act of: receivingthe at least first and second lighting commands via a network connectionbased on at least one network address.
 65. The method of claim 63,further comprising an act of: providing the at least first and secondlighting commands such that the single calibrated color produced in theact e) is a calibrated substantially white color.
 66. The method ofclaim 62, wherein the acts a) and b) include an act of controlling theat least one first LED and the at least one second LED using a pulsewidth modulation technique, wherein the at least first and secondcommands represent respective duty cycles of pulse width modulationsignals used to control the at least one first LED and the at least onesecond LED.
 67. The method of claim 63, wherein the act e) comprises anact of: passing the first and second radiation through an at leastpartially transparent material so as to mix the first and secondradiation.
 68. The method of claim 62, wherein: the act c) includes anact of applying at least one first calibration value to the firstlighting command to provide the first calibrated intensity; and the actd) includes an act of applying at least one second calibration value tothe second lighting command to provide the second calibrated intensity.69. The method of claim 68, wherein the act of storing comprises an actof: storing at least the at least one first calibration value and the atleast one second calibration value in the memory.
 70. The method ofclaim 68, wherein: the act of obtaining at least one output measurementfor the light output generated by the at least one LED includes an actof measuring the first radiation and the second radiation; and the actof formulating at least one calibration value includes acts of:determining the at least one first calibration value by comparing themeasured first radiation to at least one first reference value; anddetermining the at least one second calibration value by comparing themeasured second radiation to at least one second reference value. 71.The method of claim 70, further comprising an act of: providing the atleast first and second lighting commands so as to generate a calibratedsubstantially white color.
 72. The method of claim 62, wherein the firstlighting command includes a first reference signal, and wherein the actc) includes an act of: c1) determining at least one first calibrationvalue such that the first radiation is generated at a first referenceintensity when the first lighting command is the first reference signal.73. The method of claim 72, wherein: the act of generating light outputfrom the at least one LED includes an act of asserting the firstreference signal; the act of obtaining at least one output measurementfor the light output generated by the at least one LED includes an actof measuring the first radiation generated in response to the firstreference signal; the act of comparing the at least one outputmeasurement to at least one reference value includes an act of making acomparison of the measured first radiation and at least one firstreference value; and the act of formulating at least one calibrationvalue includes an act of determining the at least one first calibrationvalue based on the comparison.
 74. The method of claim 72, wherein theact of storing comprises an act of: storing at least the at least onefirst calibration value in the memory.
 75. The method of claim 72,wherein the act c) further includes an act of: c2) applying the at leastone first calibration value to at least one subsequent first lightingcommand to provide the first calibrated intensity.
 76. The method ofclaim 75, wherein the second lighting command includes a secondreference signal, and wherein the act d) includes an act of: d1)determining at least one second calibration value such that the secondradiation is generated at a second reference intensity when the secondlighting command is the second reference signal.
 77. The method of claim76, wherein: the act of generating light output from the at least oneLED includes an act of asserting the second reference signal; the act ofobtaining at least one output measurement for the light output generatedby the at least one LED includes an act of measuring the secondradiation generated in response to the second reference signal; the actof comparing the at least one output measurement to at least onereference value includes an act of making a comparison of the measuredsecond radiation and at least one second reference value; and the act offormulating at least one calibration value includes an act ofdetermining the at least one second calibration value based on thecomparison.
 78. The method of claim 76, wherein the act of storingcomprises an act of: storing at least the at least one secondcalibration value in the memory.
 79. The method of claim 76, wherein theact d) further includes an act of: d2) applying the at least one secondcalibration value to at least one subsequent second lighting command toprovide the second calibrated intensity.
 80. The method of claim 79,further comprising an act of: providing the at least first and secondlighting commands so as to generate a calibrated substantially whitecolor.
 81. The method of claim 79, wherein: the acts a) and b) includean act of controlling the at least one first LED and the at least onesecond LED using a pulse width modulation technique, wherein the atleast first and second commands represent respective duty cycles ofpulse width modulation signals used to control the at least one firstLED and the at least one second LED; and the acts c) and d) include anact of applying the at least one first and second calibration values tothe at least first and second commands so as to adjust the respectiveduty cycles of the pulse width modulated signals.
 82. The illuminationdevice of claim 25, wherein the processor includes calibration means foradjusting the light output of at least some LED sources of the pluralityof LED sources, based on the at least one calibration value, such thatthe additive mixture of colored light has a calibrated color.
 83. Theillumination device of claim 82, wherein the additive mixture of coloredlight is a substantially white light, and wherein the calibration meansis configured to adjust the light output of at least some LED sources ofthe plurality of LED sources, based on the at least one calibrationvalue, such that the additive mixture of colored light has a calibratedsubstantially white color.
 84. The illumination device of claim 82,wherein the calibration means includes means for compensating forperceptible differences in light output between similar illuminationdevices.
 85. The illumination device of claim 82, wherein thecalibration means includes means for scaling the light output of atleast some LED sources of the plurality of LED sources so as to producethe calibrated color.
 86. The illumination device of claim 82, whereinthe calibration means includes means for adjusting commands sent to atleast some LED sources of the plurality of LED sources, based on the atleast one calibration value, so as to produce the calibrated color. 87.The illumination device of claim 86, wherein the means for adjustingcommands includes means for applying the at least one calibration valueto at least one command sent to at least some LED sources of theplurality of LED sources.
 88. The illumination device of claim 87,wherein the processor is configured to control the plurality of LEDsources via a plurality of pulse width modulated signals, wherein the atleast one command relates to at least one parameter of at least onepulse width modulated signal of the plurality of pulse width modulatedsignals, and wherein the processor is configured to apply the at leastone calibration value to the at least one command so as to adjust the atleast one parameter of the at least one pulse width modulated signal.89. The illumination device of claim 88, wherein the at least oneparameter includes a duty cycle of the at least one pulse widthmodulated signal, and wherein the processor is configured to apply theat least one calibration value to the at least one command so as toadjust the duty cycle of the at least one pulse width modulated signal.90. The illumination device of claim 89, wherein: the processor isconfigured as an addressable processor to be coupled to a networkconnection, the processor further being configured to receive the atleast one command from the network connection based at least in part onan address of the processor.
 91. The illumination device of claim 90,wherein the at least one command is communicated over the networkconnection using a DMX protocol, and wherein the processor is configuredto receive the at least one command using the DMX protocol and to applythe at least one calibration value to the at least one command based atleast in part on the DMX protocol.
 92. The illumination device of claim82, wherein the at least one reference value is based on at least onemeasurement of an ambient lighting condition.
 93. The illuminationdevice of claim 92, wherein the calibration means is configured toadjust the light output of at least some LED sources of the plurality ofLED sources, based on the at least one calibration value, such that theadditive mixture of colored light approximates the ambient lightingcondition.
 94. The illumination device of claim 93, wherein the additivemixture of colored light is a substantially white light, and wherein thecalibration means is configured to adjust the light output of at leastsome LED sources of the plurality of LED sources, based on the at leastone calibration value, such that the additive mixture of colored lighthas a calibrated substantially white color.
 95. The illumination deviceof claim 84, wherein the illumination device is configured to be placedin a lighting network including at least one other illumination device,and wherein the processor is configured to adjust at least one firstillumination property of the illumination device so that it is similarto at least one second illumination property of the at least one otherillumination device of the lighting network.
 96. The illumination deviceof claim 95, wherein the processor is configured to adjust the at leastone first illumination property based at least in part on at least oneof an age of the at least one other illumination device, a manufacturingdate of the at least one other illumination device, and at least onemeasured illumination condition of the at least one other illuminationdevice.